Display device employing polarized light



My16, 1939. E, H, LAND 42,158,129

DISPLAYl DEvLcE v111112110111111v 'Pommz LIGHT Filed J'me 1, 1938 I //VENTU Edwin H. Land, Wellesley Farms, Mass., assignor,

by mesne assignments, to Polaroid Corporation, Dover, Del., a corporation of Delaware t Application June 1,

193s, serial l1510.211478 15 Claims. (Cl. 40-130) This invention relates to optical apparatus such as a display device employing polarized light, and morespecifically a device of the character described giving color effects.

In general, it is an object of the invention to provide a device of the character described which will efliciently perform the purposes for which it is intended, which is simple and economicalv4 of construction, whichcan be expeditiously, conveniently and safely manipulated, and which can be readily manufactured and assembled.

Other objects of the invention are to provide an article having a design thereon, the colors of which change with relative changes in position of the eye of an observer and/or the article; to provide such an article which is opaque and which may be iiexible; to provide the material of the design ready to be applied to the base of the article; and to provide such design material as laminated film which may be flexible. Y

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises an article of manufacture possessing the features, properties. and relation of elements which will be exem-` plied in the article hereinafter described and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawing, in which: i

Figure 1 is a .perspective view of an article ernbodying one form of the invention; A

Vv`Fig. 2 is a view in section of some of the elements of the article shown in Fig. 1; and

Fig. 3 is a perspective view of a modification of the article shown in Fig. 1.

Figure 1 shows an article presenting a surface having a design associated therewith. To the eye of a stationary observer, different portions of the design appear in different colors. 1f the observer moves, or if the article'is' moved with respect to a stationary observer, the respective colors of the several portions change.

In the drawing, I0 denotes a reflectingsurface of an article. There is a designl associated with this surface. The design may take any form and is shown in Fig. 1 illustratively as the letter A, which has the reference numeral I2. The various parts of the design eement I2 may be made up of a laminated strip'Id, shown in section in Fig. 2. This strip may comprise birefringent material I6, for example Cellophane or Cellophane-like material, or a' birefringent plastic `or resin, or any other birefringent material, such for example as the birefringent materials specified in my issued United States Patent No. 2,018,214 at page 2, lines 13 to 19 inclusive.

On one surface ofthe layer lli 'there is provided a second layer or film I8 of light-polarizing material. This may be in the form of 4a sheet containing optically oriented light-polarizing` crystals, such for example as the material sold under y 10 the trade name Polaroid, or it may bein the form of a coating of oriented crystalline polariz? ing material on the layer I8, such as the coating described in United States `Patent No. 2,087,795. Any structure providing a light-polarizing surface l5 on a birefringent supporting layer is deemed to be within the scope of myL invention. Preferably, the polarizing axis of the surface shouldbe angularly lpositioned with respect to a principal `optical direction of the birefringent layer. f f l On the other face of the birefringent layer I8, and opposite to the polarizing layer I8, there mayk be a layer of adhesive 20. This adhesive may be of a latex type, or it may comprise 'a resin, or may be of any other suitable material. The entire strip may be relatively thin and have the appearance of the'material sold as Scotch tape. The adhesive layer 20 is used to cause the tape to adhere to the surface lll. I

The surface I0 may be any light-reflecting surf` 30 face, such as a mirror surface, or the surface of a paper covered by foil, or the like, orl a metallic surface, such as a metallic foil supported'or not," as desired, upon 'some rigid or flexible material such as glass, paper, leather, and the like.

Light incident on the exposed face of the, polarizing surface I4 and traversing that surface is polarized. This polarized light then traverses the birefringent layer I6, impinges upon the rea fleeting surface III, again traverses the birefrin`` o gent layer I6, and impinges upon the under-surface of the polarizing layer I8, through which it passes to the eye of an observer. It will rthus be apparent that in operation the device of` the present invention provides a structure vsuch that light traversing the device traverses successively a light-polarizing element, a birefringent element, and a light-polarizing element.' The reflecting surface I0 is utilized'to insure the double use of the'polarizing ysurface I8 as both a polarizer for 50 the incident light and an analyzer for the reflected light. The birefringent'layer is traversed twice by the incident and reflected light, and it will be apparent that slight differences in the relative position of an observer andthe design on ing designs may be I Il overlies the surface l0 will result in substantially increased path lengths through the birefringent material of light reaching the eyes of the observer.

If the polarizing axis of the surface I8 is nonparallel and non-perpendicular to l principal optical direction of the birefringent layer l5, vivid colors will be imparted to the reflected light. In this connection reference is made to my issued United States Patent No. 2,018,214. patented October 22, 1935, for Advertising display device, for a fuller discussion of the optics involved in a somewhat similar device.

It will be apparent that many diverse and strikproduced, all of which are visible in reflected light and all of which com-V prise essentially a. light-polarizing surface, a birefringent layer, and a reflecting layer. These designs may be produced at small cost, if adevice such as is shown in Figs. 1 and 2 is employed, without wasting any of the polarizing or birefringent material. The reflecting surfacemay be supplied by a cheap metallized paper, such as is used for example in fancy wrappings or the like, and vthe applied birefringent and polarizing material may be flexible and may conform to the.

shape taken by the paper when in use. Such material may befeasily shipped,cut to size, and employed in a wide range of commercial applications. 'v y Furthermore the device shown in Figs. 1 and 2 is eminently suited for car card displays, bill boards and the like, where vivid spot designs may be amxed to reflecting surfaces, and where the colors of the/designs mayschange rapidly, even without any moving parts, as an observer moves past the display. the display is an out-of-doors sign. y

'I'he strip shown in Fig. 2 may be supplied in roll form as is adhesive tape, and it may be employed by an artist or other workman in the production of designs on reflecting surfaces already in place by afllxlng the strip to the surface at the place of use. It will be apparent that if sections of the strip are positioned angularly with respect to each other on the reflecting surface, each sec-1 tion will'give a different color to an observer.

In Fig. 3 there is shown a modification of the invention. In this form the birefringent layer substantially theentire surface of the reflecting element H0. 'I'he light-polarizing surface I I B may be formed by applying light-polariz- .ing material in a predetermined design to the birefringent layer. SuchA a design may be formed for example in the manner vdescribed in greater detail in the copending application of Land and lMahler, Serial No. 207,182, flied May 11, 1938.

In this form of theV invention the elements I I0, I I6 may take the form of a laminated sheet of Cellophane or Cellophane-like material to a metallized paper backing, with the Cellophane adhesively afllxed to the reflecting surface of the paper, or, as previously mentioned, the reflecting surface may comprise any other suitable means, and the birefringent layer may be laminated thereto or affixed, or merely in contact therewith.

It is also to be understood that in any form of the invention described the elements may be separate and out of contact with each other, although a unitary laminated structure is preferred.

While in the forms polarizing surface, it is to design may be effected by For example, if a reflecting sur- No light source is required if i v of the invention heretofore described the design has been spoken of as formed face having affixed thereto sections of birefringent material so as to forni a design thereon, the

entire element, including those portions of the reflecting surface not covered by the birefringent material, might be coated with a light polarizing layer. Such a structure is to be deemed to fall within the scope of my invention. It will be understood therefore that while preferably the design formed upon the reflecting formed in the polarizing layer, it may in either or both the polarizing and birefringent layers.

Since certain changes may be made inthe above article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination, a birefringent element, means on one surface thereof forming a lightpolarizing surface having its polarizing axis angularly positioned with respect to a principal optical direction of said birefringent means, and an adhesive on the opposite surface of said birefringent means. s

2. In combination, a thin, flexible strip of birefringent material having one surface coated with adhesive and the opposite surface coated with a polarizing layer having its polarizing axis angularly positioned withrespect to a principal optical direction of said birefringentstripl f 3. A transparent tape comprising a birefringent l5.V A display device comprising means providing a reflecting surface, birefringent means positioned adjacent said surface and adapted to intercept predetermined light rays incident thereonand reflected therefrom, and light-polarizing means positioned 4adjacent `said birefringent means and on that side thereof farthest from said reflecting surface to intercept said rays, said surface-providing means, said birefringent means, and said light-polarizing means being bonded together to form a unitary structure.

' 6. A display device comprising means providing a reflecting surface, birefringent means positioned adjacent said surface and adapted to intercept predetermined light rays incident thereon and reflected therefrom, and light-polarizing `means positioned adjacent said birefringent means and on that side thereof farthest from said reflecting surface to intercept said rays, said light-polarizing means comprising polarizing areas adapted to form a predetermined design.

'7. A display device comprising means providing a reflecting surface, ,birefringent means positioned adjacent said surface and adapted to intercept predetermined light rays incident thereon and reflected therefrom, and light-polarizing means positioned ing material being bonded together to form aA adjacent said birefringent means and on that 'side thereof farthest from said reflecting surface to intercept said rays, said birefringent means being bonded to said lightpolarizing means and forming therewith a predetermined design.

8. Anew article of manufacture comprising a light-polarizing lm, a birefringent film, and means providing a reflectingl surface, the hirefringent film being positioned between the surface and the polarizing film and `underlying the polarizing film, at least one of said films being in the form of a design.

9. A new article of manufacturecomprising a light-polarizing film, a birefringent film, and means providing a reflecting surface, the birefringent film being positioned between the surface and the polarizing film and underlying the polarizing film, both of said films being in the form of a design.

10. A display device comprising, in combination, a paper support having a light-reflecting surface, birefrlngent material applied to said surface, and light-polarizing material overlying said birefrlngent material.

11. A display device comprising, in combination, a paper support having a light-refiecting surface, birefringent material applied to said surface, and light-polarizing material overlying said birefringent material, said reflecting paper, said birei'ringent material, and said light-polarizunitary structure.

12. In combination, opaque supporting means having a reflecting surface, birefringent means affixed to said surface, and light-polarizing means affixed to the opposite surface of said birefringent means, all of said elements forming a unitary structure.

13. In combination, opaque supporting means having a reflecting surface, blrefringent means affixed to said surface, and light-polarizing means affixed to the opposite surface of said birefringent means, all of said elements forming a unitaryl structure, said light-'polarizing means'pmprising light-polarizing areas forming a design and having their polarizing axes parallel and at a predetermined angle with a principal optical i direction of said birefringent means.

14. In combination, means providing a metallic refiecting surface, a birefringent film adhesively secured to said surface, and a film of light-polarizing material positioned against at least a part of said birefringent film.

l5. In combination, a film of birefringent material, a metallic film secured to one surface of said birefringent lm and a film of light-polarizing material spread over at least 'a portion of the opposite surface of said birefringent film.

EDWIN H. LAND. 

